Radio frequency (RF) catheter ablation is an invasive procedure used to remove faulty electrical pathways from patients who are prone to develop cardiac arrhythmias such as atrial fibrillation (AF). In AF ablation procedures, complete electrical isolation of the pulmonary veins is targeted and this is achieved by creating lesion lines with an ablation catheter.
The majority of the catheter ablation procedures are performed with “single-point ablation catheters”. Lesion lines can be created with such catheters by sequential point by point ablation. To achieve complete electrical isolation of the pulmonary veins lesion lines are created meeting the two requirements of being transmural and continuous.
A requirement for RF catheters is a more adequate control. A system that can provide a real-time feedback of the lesion development in the tissue, and can provide real-time information about the depth of the lesion with respect to the thickness of the tissue at the treatment site, would prevent injury and potential death from overheating in (RF) catheter ablation procedures, while insufficient heating results in recurrence of arrythmia. It has been shown that high-frequency ultrasound can be used to monitor the progression of the lesion boundary in M-mode imaging.
Embedding ultrasound transducers in ablation catheters enables real-time feedback on lesion front progression.
U.S. Pat. No. 7,846,101 discloses an intravascular ultrasound imaging apparatus comprising a transducer assembly. The assembly includes a flexible circuit comprising transducer elements attached to a flexible substrate. However, as the flexible substrate is part of the material stack forming the assembly, the flexible foil may produce acoustical effect adverse to the transducer elements performance.
The inventor of the present invention has appreciated that an improved transducer assembly is of benefit, and has in consequence devised the present invention. In particular it would be advantageous to realize a transducer assembly having acoustic properties depending only on the transducer element material. It would also be desirable to enable the user of RF catheter to access real-time feedback of the lesion development in tissue during RF catheter ablation procedure.